EP0500555B1 - Process for manufacturing tooth replacements by spark erosion and device for clamping, inserting and truing plaster models or copper electrodes for the spark-erosion manufacture of tooth replacements - Google Patents

Abstract

The invention relates to a process for manufacturing tooth replacements like crowns or bridges involving the making of a positive wax model, the manufacture of spark erosion electrodes, the inner surface of which has the negative outline of the wax model and the spark-erosion machining of a blank to form a tooth replacement. Especially to prevent the wax model from being damaged during the various machining processes and to improve the finished accuracy of the spark erosion electrodes, it is proposed to coat the tooth stump with a plastic cap before making the wax model and also to apply several layers of plastic to the wax model over the tooth centreline, the uppermost of which is secured to a guide plate by curing the plastic concerned. After removal from the plaster model the copper spark erosion electrode concerning the apex section is made and then this electrode is released with the contacting wax model and the plastic electrode for the closed side. The invention also relates to a device for clamping, inserting and truing plaster models or copper electrodes. This device has in particular a cantilever arm with vertical drillings, a magnetic underside and suitable fitting and clamping devices to take pins. The cantilever arm may be raised and lowered and is arranged opposite a bench having a clamping device for a plaster model and/or a recess to take galvanically made copper electrodes. It is possible with this device to make precise axial and radial adjustments, thus ensuring highly accurate manufacture.

Description

Process for the production of dental prosthetic items by means of spark erosion and device for clamping, inserting and aligning plaster models or copper electrodes for the spark erosive manufacturing of dental prosthetic items

The invention relates to a method for producing tooth replacement parts, such as crowns or bridges, according to the preamble of claim 1

Such a method is described for example in EP-A-0 225 513.

The invention further relates to a device for clamping, inserting and aligning plaster models or copper electrodes for the spark-erosive manufacture of dental prostheses, comprising a storage table which can be adjusted to any desired inclination.

Already in the German Dental Journal, 41, pages 525 to 526 (1986), the production of a metal sleeve crown from solid material using spark erosion is described. Here, a wax mold individually modeled on a model or in the patient's mouth is galvanically coated with an approximately 1 mm thick copper layer above and below a crown equator assumed in one plane. This galvanoplastic can be separated at the equator, so that two formula electrodes are obtained with which a dental prosthetic item is manufactured from a metal blank using electrical discharge machining. Both formula electrodes penetrate into the metal body in accordance with the erosive removal and thereby form the tooth replacement part, for example a jacket crown. The advantage of this method is that conventional noble metal and non-noble metal alloys can be processed, especially those that cannot be cast or can only be cast under difficult conditions. In the manufacture of dental prostheses, errors resulting from changes in shape, dimensions and structure during casting are largely excluded. A disadvantage of this method is, however, that the natural tooth or correspondingly shaped wax models have no clearly definable equatorial plane, since the tooth equator is undulating both in the vertical and in the horizontal direction. If you assume a medium cutting plane, then undercuts are accepted that cannot be machined by means of spark erosion.

In addition, it is proposed in DE 37 35 558 C2 to arrange the positive wax models on a common carrier, in such a way that casting molds can be produced and shaped. The individual spare parts are to be aligned in a common equatorial plane, namely in their widest horizontal sectional plane, this equatorial plane being the parting plane for the later eroding electrodes. In a further process step, the spaces between the individual spare parts are filled up to this assumed equatorial plane in order to first produce the upper electrode, with one or more orientation pins being arranged perpendicular to the equatorial plane when the spaces between the individual denture wax models are filled. After the casting compound has hardened, for example a silicone mixture, as the surface is freed of impurities, the cleaned model is coated with a thin layer of silver, which serves as a conductive layer for the later eroding electrode. After galvanic copper application, this is stabilized by a rear triangle and can be used as an erosion electrode. To produce the second electrode, the first model is rotated through 180 °, entered into a mold which is filled with a hardening carrier mass in the base area. After the carrier mass has hardened, a silver layer is also applied to the surface and this is coated with copper. The disadvantage here is that an arbitrary equatorial plane, as set out above, is assumed, furthermore the individual wax models have to be aligned in a casting mold, which in part can only be achieved by underlaying Spacers that have to be manufactured in addition. Time savings in spark erosion, as desired, cannot be achieved because only a predetermined number of erosion sparks - depending on the voltage applied - can be generated per unit of time.

Overall, the previously described methods have the further disadvantage that the wax models are unprotected both when pulling off the plaster model and during the preparation or manufacture of the copper electrodes, and the risk of deformation must be accepted. The prior art provides nothing about the exact alignment of the wax models or the copper electrodes to one another.

It is therefore an object of the present invention to further develop the aforementioned method in such a way that, regardless of the manual skill of the processing person, it is ensured that the wax model remains undamaged during the various processing steps and that measures are given, such as an exact alignment of the plaster model and the Copper electrodes can be guaranteed to each other. It is also an object of the present invention to provide a suitable device for carrying out this alignment.

In the method mentioned at the outset, the object is achieved in that a lubricious, stable, as inelastic, thin-walled plastic hood is applied to the degreased, impregnated stump of the plaster model, which ends just above the preparation margin and over which the wax model then forms a preparation margin and simultaneous definition of the tooth equator is formed before a silicone layer reaching to the tooth equator is applied occlusally, the plaster model being clamped and aligned as a master model with an inserted wax part in an adjusting device, that further on the silicone layer a curable plastic is applied, onto which a horizontally oriented, larger circumferential orientation plate is lowered, so that this orientation plate is connected to the plastic after the plastic has hardened, that this orientation plate together with the adhering layers is lifted off the plaster stump and from the apical On the side of the tooth equator, the last applied plastic and the adjoining surface of the orientation plate are filled and the electrically conductive material is applied to the apical side of the first plastic hood, the exposed wax model surfaces and adjoining areas up to the orientation plate, and a copper coating is then applied galvanically . The copper application is then removed together with the wax model and, from the occlusal side to the tooth equator, a conductive material is also first applied and then a copper coating is applied to it by electroplating. On both sides of the copper coating, a mandrel or other suitable fastening means is attached to the outer surfaces, the mandrels being aligned with one another in the axial and radial directions.

The previous degreasing and impregnation of the die as well as the application of the thin-walled plastic hood serve to protect the wax model from the inside, so that no deformation of the wax model can occur, especially when the wax model is pulled off the plaster model.

The tooth equator of the modeled wax model is exactly determined and its actual course is taken into account when applying the silicone layer. In order to prevent the wax model from being removed by hand from the master model (plaster model), a hardenable plastic is also applied to the silicone layer, onto which a horizontally oriented orientation plate is lowered, so that this orientation plate can be used after the plastic has hardened the plastic is connected. If you lift this orientation plate together with the adhering layers from the plaster stump, this can be done by applying a force to the orientation plate, which prevents pressure forces from the side or from above acting on the wax model when you touch it. The filling of the last applied plastic layer is used for smoothing and above all for filling up any undercuts that may still be present, which would prevent the finished copper electrode from being pulled off after galvanic copper plating. In addition, the plastic is selected with regard to the silver or graphite layer to be applied afterwards. The copper application, which will later be used as a spark erosion electrode, represents an exact negative contour of the plaster stump and the apical part of the wax-up.

After this copper application has been removed from the silicone layer together with the wax model, a silver or graphite layer is also applied to the exposed occlusal side up to the tooth equator, after which a copper layer is produced by electroplating. The lower apical copper electrode can be galvanized together with the occlusal copper electrode.

In order to be able to clamp the copper electrodes in a spark erosion machine, they have to be provided with fastening means, either plates, spikes or guide sleeves, on the back of each. It is important that the fasteners are aligned both in the axial (horizontal and vertical direction) and in the radial direction. This means that in the case of nested copper electrodes, the longitudinal axes of the mandrels or fastening means must lie on one line and it must also be ensured that the second electrode is not opposite in the event of subsequent erosion the first is twisted in the radial direction. It is therefore advisable to use such parts as fastening means that are not rotationally symmetrical, that is to say, for example, mandrels with a semicircular cross section or non-round plates.

Developments of the method are described in claims 2 to 14.

A cold polymer based on acrylate has proven to be particularly suitable as the material for the plastic hood. The plastic hood should preferably end approx. 1/10 mm above the preparation margin in order to enable clean wax modeling in the area of the preparation margin.

For reasons of cost, the orientation plate is made of metal and has at least two holes through which this plate can be adjusted.

In order to protect the wax model from damage when it is lifted off the plaster stump (master model), such as may occur due to tilting or twisting when removed by hand, the orientation plate is magnetically attached to a horizontal extension arm of an adjustment device both during lowering and during removal from the master model held. This ensures exact vertical guidance in the direction of insertion.

If you want to carry out the electrical discharge machining first with a roughing electrode and fine machining with a finishing electrode, the following manufacture of the roughing electrode is recommended. First, as described above, a 2 to 3/10 mm thick copper layer is applied galvanically apically or occlusally. This layer is then passivated on its surface facing the bath, whereupon a new layer of conductive material is applied and the electroplating is continued. The 2 to 3/10 mm thick copper layer can then be removed, which causes results in a negative contour of the copper electrode suitable for roughing.

As already mentioned, silver or graphite is preferably used as the conductive material, which is applied in the thinnest possible layer thicknesses of 1 to 5 μm.

The spark erosion electrodes should be as small as possible for reasons of material savings and a short erosion time. On the other hand, it is imperative that the copper halves of the electrodes extend into an area where the two halves lie flat against one another, that is, as a rule, there is a common ring contact surface. This common ring surface is therefore preferably connected via individual webs to the actual copper electrode, which has the negative contour of the wax model, which can be done by applying appropriate silver or graphite layers.

To align the fasteners for the spark erosion machine and attach them to the galvanically produced copper electrodes, these copper electrodes are inserted into a correspondingly shaped recess with a horizontal support surface of a support table, axially and radially aligned, before a mandrel clamped in a cantilever arm and also radially aligned with one end attached plate is lowered onto the copper electrode surface and finally the plate is glued or soldered to the surface. Axial alignment of the mandrel or of the plate fastened to it at the end can be carried out by means of appropriately arranged clamping devices of a cantilever arm above the table. The axial alignment of the copper electrode inevitably results from the recess. A radial alignment of the copper electrode is possible through an asymmetrical contour and a correspondingly adapted recess. Alternatively, however, it is also possible to use the connecting means, such as mandrels, Manufacture plates, sleeves or the like, galvanoplastic together with the copper application for the spark erosion electrode as a one-piece part in a single operation, so that an additional operation, such as gluing or soldering, is omitted.

In order to always obtain the same reference lines, the recess of the table consists of an annular flat surface and a crater that is large enough to accommodate a copper electrode.

Since only 0.5 to 0.7 mm copper of the copper electrode is used for spark erosion for reasons of stability, the copper electrode is preferably only electroplated until the copper electrodes have a thickness of up to 1 mm.

The device described in claim 15 is used for clamping, inserting and aligning plaster models or copper electrodes for the spark-erosive manufacture of dental prosthetic items. On the one hand, this consists of a storage table that can be adjusted to any desired inclination, above which a horizontal cantilever arm, which is articulated on a vertical column, is arranged, which can be moved up and down and rotated about the longitudinal axis of the column or pivoted over a partial area. This column and the storage table each have at least one bore for receiving a centering mandrel, with which the extension arm can be adjusted in the vertical-axial direction with respect to the storage table. Furthermore, the cantilever arm has a permanently magnetic or magnetically excitable receiving surface for a perforated metal orientation plate on its underside.

To clamp a plaster model, the storage table has clamping jaws and / or a recess on its surface at least one flat ring surface for receiving a galvanically produced copper electrode.

Preferably, the area of the support table support surface enclosed by the ring surface is hollowed out in a crater-shaped manner, which makes it possible to insert the assembled electrode halves removed from the bath and to first solder or glue a fastening means to the first upper electrode after appropriate alignment, then the copper electrode pair by 180 ° to rotate and attach a corresponding attachment to the second electrode. For example, plates which are preferably fastened to the end of a mandrel can be used as fastening means, this mandrel being received in a tensioning or clamping device or in a bore of the extension arm provided with an internal thread.

The storage table preferably has removable interchangeable upper parts, one of which is provided with a clamping device for aligning a master model (plaster model) and the other with a recess for receiving a galvanically produced copper electrode.

Fig. 1a, b

jeweils einen Querschnitt durch einen Gipsstumpf mit angeformtem Wachsmodell, worauf verschiedene Überzüge aufgetragen worden sind, in schematischer Darstellung,

Fig. 2a, b

jeweils einen Querschnitt durch ein Wachsmodell mit galvanisch hergestellter Kupferformelektrode an der apikalen Seite,

Fig. 3a, b

jeweils einen Querschnitt durch aufeinandergesetzte Kupferformelektroden mit dazwischenliegendem Wachsmodell,

Fig. 4 und 5

jeweils schematische Darstellungen der erfindungsgemäßen Vorrichtung und

Fig. 6

eine Darstellung des funkenerosiven Verfahrens zur Herstellung einer Krone.

Exemplary embodiments in which the invention is to be further explained are shown in the drawings. Show it

Fig. 1a, b

each a cross section through a plaster stump with a molded wax model, on which various coatings have been applied, in a schematic representation,

2a, b

each a cross-section through a wax model with an electroplated copper electrode on the apical side,

3a, b

each have a cross section through stacked copper electrodes with a wax model in between,

4 and 5

each schematic representations of the device according to the invention and

Fig. 6

an illustration of the spark erosive method for producing a crown.

• 1. die zahntechnische Bearbeitung - Herstellung eines Wachsmodelles
• 2. um die Herstellung einer Galvanoplastik und
• 3. den funkenerosiven Abtrag aus einem Rohling.

The method according to the invention combines three different technologies, each of which can be carried out without specific specialist knowledge. The technologies are

• 1. Dental processing - production of a wax model
• 2. to manufacture a galvanoplastic and
• 3. the spark erosive removal from a blank.

Disadvantages, such as the formation of pores, cavities or changes in shape are excluded when carrying out the method described below.

In the manufacture of dental prosthetic items, an impression tray is used, from which a positive plaster model is produced in a manner known in the art. The plaster stumps are created according to this plaster model - either for crowns or for bridges - each with correspondingly defined preparation limits.

The plaster stump 10 is cleaned and impregnated. After the impregnating agent has dried on, a plastic hood 11 made of cold polymer based on acrylate is applied, which is about 1/10 mm ends above preparation margin 12. This plastic hood has a thickness of 0.5 to about 1 mm. The acrylic cap 11 has the advantage that no deformation of the wax model 13 can occur in subsequent operations. At the same time, the desired electrode is duplicated - for the production of roughing electrodes and finishing electrodes.

The wax-up is the basis for manufacturing electrodes. The crown or bridge models must be modeled so that the preparation margin 12 and the tooth equator 14 are optimally displayed. The plaster stump 10 with the modeled wax crown 13 is then inserted into the master model and screwed into a model table. All important points are now checked with a parallelometer, as is customary in the state of the art. Thereafter, a thin silicone pad 15 must be applied to the wax model 13 above the tooth equator, which covers that the wax crown 13 is not deformed and does not stick after further operations. The model table is then placed under an adjustment device so that the axis and the size of the blank can be determined for inclusion in the spark erosion machine. A curable plastic 16 is applied above the silicone pad 15, and an orientation plate 17 made of metal is lowered onto it before this plastic 16 hardens, so that this metal plate 17 is firmly connected to the plastic 16 after it has hardened. Then the orientation plate 17 together with the adhering layers 16, 15, 13 and 11 is lifted off the plaster stump 10 and from the apical side from the tooth equator 14 from the last applied plastic 16 and the adjoining surfaces of the orientation plate 17. The leveling compound is designated 18.

As can be seen from Fig. 2a, the underside of the orientation plate 17, the filler 18, the exposed wax surface 13 below the equator 14 and the inside of the cap 11 is then coated with a silver layer 19 from the apical side, which forms the basis for the copper plating 20 serves. For this purpose, the orientation plate is optionally placed together with other orientation plates of other models in an investment material or otherwise attached to a support and placed in a galvanic bath. The galvanic copper coating should have a thickness of approximately 1 mm. The orientation plate together with the layers 16, 15, 18 is then lifted off, so that the copper coating 20 produced is obtained with the wax model 13 still in place, which is accessible from the occlusal side. A silver or graphite layer 21 is now applied to this wax model 13 and the adjoining edge regions of the copper coating produced, which layer serves as the base of a copper layer 22, which is likewise produced in a galvanic bath. For this purpose, the entire body shown in FIG. 3a is in a galvanic bath. After applying a sufficiently thick copper layer 20 or 21, the body is removed from the galvanic bath and the wax model is removed, since it is no longer required. The inside of the copper coatings 21 and 20 correspond to the negative contour of the wax model 13. In order to be able to use the copper parts 20, 21 as spark erosion electrodes, a fastening means must now be attached to the outside. This fastening means can consist of a mandrel to be soldered or a plate or the like. It is only important that the fastening means is attached in such a way that it is aligned both axially and radially, ie the fastening means used must have the same orientation with respect to the longitudinal axis 23 shown in FIG. 3a.

The cross sections shown in FIGS. 1b, 2b and 3b differ from those described above in that the connecting means are also produced by electroplating, together with the copper application serving as a later spark erosion electrode as a one-piece part.

As can be seen from Fig. 1b, with the aid of the device indicated in Fig. 5 37 guide sleeves or mandrels, e.g. made of brass (brass tube 38), waxed on the wax model 13 or the layers 15, 16 and / or 18 applied thereon.

As illustrated in FIG. 2b, however, the silver layer 19 is applied up to the brass tubes 38 and slightly overlapping them, whereupon a continuous copper coating 20 is subsequently applied galvanically. After lifting off the orientation plate 17, prior to the galvanization of the occlusal side, rods 39 are first pushed through the brass tubes 38 for alignment and the silver layer 21 is applied to the area of the tubes 38 on the occlusal side, whereupon the copper layer 22 is then galvanized. In order to create a fastening in the spark erosion system, the ends of the tubes are preferably left free, approximately over a length of approximately 5 mm, which can be brought about by covering these ends before the copper plating.

With the manufacturing technology shown in FIGS. 1b to 3b, the connecting means can be produced together with the copper coatings in a single work step, so that gluing or soldering to the copper electrode is not required.

A device for clamping a master model 24 and its alignment is shown in FIG. 4. This device essentially consists of a storage table 25 which can be pivoted in the desired spatial directions and which, for example, has clamping jaws 26 for clamping the plaster model 24.

A cantilever arm 27 is arranged above this table and can be moved up and down in the direction of the double arrow 28. This cantilever arm 27, like the table 25, has a bore, not shown, in the vertical direction, via which the cantilever arm and the table can be aligned in the axial direction by means of a centering pin. In addition, the underside of the cantilever arm 27 is magnetic and therefore suitable for holding an orientation plate 17. The cantilever arm 27 is either fixedly attached to a vertical column 29 rotatable about its vertical axis or rotatable about this vertical axis 29. The support table 25 can either be fixed to a base 30 or rest loosely on it.

The device shown in FIG. 5 is basically constructed in the same way, the support table 25 having an annular recess 31 which surrounds a crater 32. The body shown in FIG. 3 for aligning and attaching a fastening means can be inserted into this recess 31, 32. If a mandrel with a plate fastened at the end serves as fastening means, this mandrel 33 is fastened in a suitable clamping or clamping device of the extension arm 27. By moving the cantilever arm 27 finally the end plate 34 comes to the surface of the inserted copper part and can be soldered to it or connected to a conductive plastic. By turning the copper double part through 180 °, a fastening device can also be attached to the other side. This ensures that both fastening devices are aligned with respect to the axis 23 (see FIG. 3) and also in this respect in the radial direction, in particular it is advisable to provide the mandrel 33 with a non-rotationally symmetrical cross section. For the production of a crown made of metal, a blank 35 is assumed, onto which the copper electrode 21 is lowered until the negative contour is reached by continuous removal. Then the other Side the opposite electrode moved up and the blank 35 processed until the finished sleeve 36 is formed. EDM removal is known in principle and is explained, for example, in DE 35 44 123, to which reference is hereby made.

Claims (19)

1. A method of making tooth replacement parts such as crowns or bridges, whereby a wax model (13) of the tooth replacement part is made in a positive plaster modes (10), this wax model (13) is covered with a silicone rubber (15) occlusally up to the level of the tooth equator (14) and is subsequently apically of the removed wax model (13) as well as the bordering silicone-rubber peripheral surfaces are covered with an electrically conductive material (19) and on top of this a copper layer (20) is galvanically plated, whereupon the silicon rubber is removed from the occlusal side and the wax model (13) and the surrounding edges are coated with an electrically conductive material (21) whereupon a copper coating (21 ) is galvanically applied and subsequently the copper layers (20, 22) are separated from each other and from the wax model (13) and are used as spark-erosive electrodes for forming a tooth replacement part corresponding to the wax model from an erodible material, characterized in that
      on a degreased sealed stump (10) of the positive plaster model a thin-walled, stable, slippery, and relatively inelastic synthetic-resin cap (11) is mounted which stops on the occlusal side shortly before the preparation border (12) and over which is subsequently formed the wax model (13) by shaping a preparation border (12) and simultaneous establishment of the tooth equator (14), before a silicone layer (15) extending to the tooth equator (14) is mounted occlusally on it, while meanwhile the plaster model (13) is set as a master model with the inset wax parts in an adjustment device, that in addition on the silicone layer a hardenable plastic (16) is layered on which a horizontally extending and overreaching orientation plate (17) is set so that this orientation plate (17) is fixed after hardening of the plastic (16) with the plastic (16), that this orientation plate (17) together with the affixed plastic (16), the silicone layer (15), the wax model (13), and the plastic cap (11) is lifted from the plaster stump (10) and a filler is applied from the apical side from the tooth equator (14) to the last applied plastic (16) as well as to the adjacent surfaces of the orientation plate (17) and the apical sides of the (first) plaster cup (11), the exposed wax-model surfaces (13) and adjacent areas right up to the orientation plate (17) are coated with an electrically conductive material (19) and thereover for galvanic purposes with a copper layer (20), that the copper layer (20) together with the wax model (13) are separated and from the occlusal side right up to the tooth equator (14) first a conductive material (21) and then for galvanic purposes a copper layer (22) is applied and that on both sides of the copper layer (22) on the outer surfaces a connecting element such as a plate, a pin, or a sleeve is mounted such that they can be aligned radially and axially relative to each other.
2. The method according to claim 1, characterized in that a cold acrylate-based polymer is applied to the plaster-model stump as plastic cap.
3. The method according to claim 1 or 2, characterized in that the plastic cap stops about 1/10mm above the preparation border.
4. The method according to one of claims 1 to 3, characterized in that an orientation plate of metal preferably formed with two bores is set on the hardened plastic.
5. The method according to claim 4, characterized in that the orientation plate is held by means of a magnet on a horizontal outrigger arm of the adjustment mechanism during setting of it on the plastic and pulling it from the master model.
6. The method according to one of claims 1 to 5, characterized in that a 2 to 3/10mm thick copper layer is galvanically applied, this layer is passivated on its surface, a new layer of conductive material is applied, and the galvanic coating for forming the rough electrode is started.
7. The method according to one of claims 1 to 6, characterized in that the conductive material is silver or graphite, preferably in a thickness of 1 to 5 µm.
8. The method according to one of claims 1 to 7, characterized in that the layer of conductive material and the galvanic copper layer is only applied to all surfaces of the wax model and the regions of its coatings and thereafter is applied to several elements leading to a ring and to partial surfaces of the ring.
9. The method according to one of claims 1 to 8, characterized in that the connecting element is formed by a pin and a small plate or sleeve which are separable from the end of the plate and which are soldered, glued or galvanically united with the copper layer as a single galvanic piece.
10. The method according to claim 9, characterized in that the copper electrodes for mounting the pins are set in a correspondingly shaped recess of a table with a horizontal support surface, are axially and radially aligned before a radially aligned fitted in an outrigger arm and carrying on its end a fixed plate is set down on the copper electrode surface, and subsequently the plate is soldered to the surface or glued thereto preferably by a conductive plastic.
11. The method according to claim 9, characterized in that, before galvanic application of the copper layers on the wax model, supports are formed on the wax model for the subsequently galvanically produced connecting elements after previous axial and radial alignment and are covered with a layer of conductive material to make them conductive so that the subsequently applied copper layer for spark-erosion electrodes are unitary with the connecting elements.
12. The method according to claim 9 or 11, characterized in that the supports for the subsequently galvanically produced connecting element are sleeves whose end are covered preferably over a length of about 5mm before the application of the copper.
13. The method according to one of claims 10 to 12, characterized in that the copper electrode is laid in a recess serving as holder of an annular flat surface.
14. The method according to one of claims 1 to 13, characterized in that the galvanic coating is carried out such that the copper electrodes have a minimal thickness of 1mm.
15. An apparatus for holding, setting, and aligning of plaster models or copper electrodes for the spark-erosive production of tooth parts according to one of claims 1 to 14, comprising a holding table orientable in any desired inclination, characterized in that above the holding table an outrigger arm that is coupled on a vertical column is arranged that is movable up and down and also pivotally of the column axis or over a range such that this column and the support table each have at least one bore for holding a centering pin whereby the outrigger arm is fixable in the vertical/axial direction relative to the support table, and that the underside of the outrigger arm has a permanent magnet or magnetically excitable holding surface for an apertured orientation plate of metal.
16. The apparatus according to claim 15, characterized in that the support surface of the support table has holding jaws for clamping a plaster model and/or a recess with at least one planar annular surface for receiving a galvanically produced copper electrode.
17. The apparatus according to claim 16, characterized in that the regions surrounding the annular surfaces are hollowed out like a downwardly open recess.
18. The apparatus according to one of claims 15 through 17, characterized in that the outrigger arm has for holding a pin a tightening or clamping device or an internally threaded bore.
19. The apparatus according to one of claims 15 to 18, characterized in that the support table has removable and exchangeable upper parts of which one is provided for holding a master model and the other is provided with a recess for holding a galvanically produced copper electrode.

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